Pharmaco-nutritional strategies to increase nitric oxide signaling in Raynaud phenomenon (Nivose): a series of N-of-1 trials

Background Treatment of Raynaud phenomenon(RP) with oral vasodilators(calcium channel block-ers and phosphodiesterase type 5 inhibitors) has shown moderate efficacy, may not benefit to all patients, and adverse effects often compromise long-term treatment. In addition, a large placebo effect may jeopardize the assessment of treatment benefits. Pharmaconutritional strategies aiming at increasing nitric oxide bioavailability (beet-root juice and L-citrulline) may be promising alternatives, and we further hypothesized that patient preference for a treatment could be a driver of the response. Methods This study consisted of a series of randomized, double-blind, N-of-1 trials conducted in outpa-tients with primary or secondary RP. Each patient underwent a multiple crossover design with repeated blocks of randomized treatments periods: 2 weeks of placebo, 2 weeks of active treat-ments, and 1 week of washout. Outcomes included the Raynaud Condition Score(RCS), fre-quency and daily duration of attacks. Each patient prespecified its preferred primary outcome, efficacy threshold and preferred treatment, which was used for stratified randomization. Gener-alized linear mixed-effects models were used to determine individual and aggregated efficacy. Results Twenty-one patients completed 2 to 8 treatment blocks. Seventeen patients tested L-citrulline, 17 beetroot juice and 13 both treatments. Ten patients selected RCS as a primary outcome, 6 patients the number of attacks and 5 the duration of attacks. Me-dian threshold for considering treatment efficacy chosen by patients was 50% (min-max 20% to 75%) reduction of symptoms. Using individual criteria to define efficacy neither L-citrulline nor beetroot juice showed significant efficacy compared to baseline. Based on the aggregated data, our results show no significant difference between L-citrulline and the L-citrulline-based placebo, nor between beetroot juice and nitrate-depleted beetroot juice, with the exception of the daily duration of RP attacks with beetroot juice (p=0.002). Finally, there was a marked placebo response, notably when patients received their preferred treatment. Conclusions: Our study did not show significant beetroot juice or L-citrulline efficacy in RP. However, we found that individual preference for one treatment over another maximizes responses to both placebo and active treatments, particularly with regard to the frequency and duration of RP attacks, thus suggesting that a real and modifiable placebo effect exists in RP.